Note: Descriptions are shown in the official language in which they were submitted.
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SPHERICAL NIOBIUM ALLOY POWDER,
PRODUCTS CONTAINING THE SAME,
AND METHODS OF MAKING THE SAME
BACKGROUND OF THE INVENTION
[0001] This application claims the benefit under 35 U.S.C. 119(e) of prior
U.S. Provisional
Patent Application No. 62/778,377, filed December 12, 2018, which is
incorporated in its
entirety by reference herein.
[0002] The present invention relates to metals, in particular niobium
alloys, and products
made from niobium alloys as well as methods of making and processing the
niobium alloys.
[0003] Among its many applications, niobium alloy powder is generally used
in the
sputtering target industry, munition area, and space industry in view of its
properties.
[0004] Currently, for example, niobium alloy powders can be primarily
produced in a
mechanical process. The mechanical process includes the steps of electron beam
melting of
niobium with one or more other metals to form an alloy ingot, hydriding the
ingot, milling the
hydride, and then dehydriding, crushing, and heat treating. The niobium used
for instance in
such a process can be of the type described in U.S. Patent Nos. 6,051,044;
6,165,623; 6,375,704;
and 6,863,750; all incorporated in their entirety by reference.
[0005] Most of the efforts in developing niobium alloy powders have been
driven by the
sputtering target and/or forged metal industry, where such metals were made
for this specific
purpose only. However, one or more properties of these niobium alloys can be
generally
unwanted in industries such as in additive manufacturing. Accordingly, there
is a need and
desire to develop niobium alloy powders that can be useful in additive
manufacturing and/or
other industries.
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SUMMARY OF THE PRESENT INVENTION
[0006] A feature of the present invention is to provide a niobium alloy
powder that can be
very useful in additive manufacturing or 3D printing.
[0007] Another feature of the present invention is to provide articles,
products, and/or
components from additive manufacturing or 3D printing using niobium alloy
powder that is
easier to use and/or provides one or more improved properties in such
processes.
[0008] An additional feature of the present invention is to provide
processes to make the
niobium alloy powder as well as the articles, products, and/or components
containing the
niobium alloy powder.
[0009] Additional features and advantages of the present invention will be
set forth in part
in the description which follows, and in part will be apparent from the
description, or may be
learned by practice of the present invention. The objectives and other
advantages of the present
invention will be realized and attained by means of the elements and
combinations particularly
pointed out in the description and appended claims.
[0010] To achieve these and other advantages, and in accordance with a
purpose of the
present invention, as embodied and broadly described herein, the present
invention relates to
niobium alloy powder. The niobium alloy powder includes a spherical shape
wherein the
powder has an average aspect ratio of from 1.0 to 1.25; a purity of niobium
alloy of at least 99.9
wt% based on total weight of the niobium alloy powder, excluding gas
impurities; an average
particle size of from about 0.5 micron to about 250 microns; a true density of
from 8.2 g/cc to 20
g/cc; an apparent density of from about 2 g/cc to about 18 g/cc; and a Hall
flow rate of 20 sec or
less. The niobium alloy powder can be, and preferably is plasma heat-treated.
[0011] The present invention further relates to an article or an article of
manufacture (or
portion thereof or part thereof) made from or formed from the niobium alloy
powder of the
present invention. The article or portion thereof or part thereof can be, but
is not limited to, a
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boss for a coil set for a physical vapor deposition process, a boss that
comprises open cellular
structures and solid structures, a coil set or part thereof for a physical
vapor deposition process,
an orthopedic implant or part thereof, a dental implant or part thereof, and
other medical and/or
dental implants or portions thereof
[0012] Further, the present invention relates to a method to make the
niobium alloy powder
of the present invention. The method can include plasma heat-treating a
starting niobium alloy
powder to at least partially melt at least an outer surface of said starting
niobium alloy powder in
an inert atmosphere to obtain a heat-treated niobium alloy powder, and cooling
the heat-treated
niobium alloy powder in an inert atmosphere to obtain the niobium alloy
powder. The starting
niobium alloy powder can be an ingot derived niobium alloy powder.
[0013] In addition, the present invention relates to a method for forming
an article, wherein
the method includes the step of additive manufacturing to form the article by
utilizing the
niobium alloy powder of the present invention to form the shape of the article
or part thereof
The additive manufacturing can include or comprise laser powder bed fusion,
electron beam
powder bed fusion, directed energy deposition, laser cladding via a powder or
wire, material
jetting, sheet lamination, and/or vat photopolymerization.
[0014] It is to be understood that both the foregoing general description
and the following
detailed description are exemplary and explanatory only and are intended to
provide further
explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0015] The present invention relates to novel niobium alloy powders and to
articles (or
portions thereof) formed from the niobium alloy powders of the present
invention. The present
invention further relates to methods of making the novel niobium alloy powders
as well as
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methods to form articles (or portions thereof) utilizing additive
manufacturing techniques and
processes.
[0016] As opposed to other spheroidization technologies, plasma
spheroidization provided
the energy needed to melt the niobium alloy quickly and produces a truly
spherical powder with
high purity, and/or low oxygen, and/or minimal gas entrapment and/or a
controlled particle size
distribution (PSD).
[0017] In more detail, the niobium alloy powder of the present invention
comprises, consists
essentially of, consists of, or includes a spherical shape wherein the powder
has an average
aspect ratio of from 1.0 to 1.25; a purity of niobium alloy of at least 99.9
wt% based on total
weight of the niobium alloy powder, excluding gas impurities; an average
particle size of from
about 0.5 micron to about 250 microns; a true density of from 8.2 g/cc to 20
g/cc; an apparent
density of from about 2 g/cc to about 18 g/cc; and a Hall flow rate of 20 sec
or less.
[0018] Except for the properties set forth above for the niobium alloy
powder with respect
to spherical shape, purity, average particle size, density and Hall flow rate,
it is to be understood
that there is no other critical limitations with regard to the type of niobium
alloy powder, that
can be used in the additive manufacturing methods of the present invention as
described herein.
[0019] The niobium alloy powder of the present invention can be what is
considered a salt-
reduced niobium powder that is combined with one or more non-niobium metals
and melted to
form the niobium alloy that can be reduced to powder form or the melted metals
can be
processed into powders. In the alternative, the niobium alloy powders can be
formed from salt-
reduced niobium alloy powders such as, but not limited to, magnesium or sodium
reduced
niobium alloy powder. The niobium alloy powder can be a vapor phased-reduced
niobium alloy
or ingot-derived niobium alloy powder.
[0020] As indicated, the niobium alloy powder of the present invention has
a spherical
shape. This shape is defined by an average aspect ratio. The average aspect
ratio of the niobium
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alloy powder or aspect ratio is defined herein as the ratio of the largest
linear dimension of a
particle (i.e., niobium alloy powder) to the smallest linear dimension of the
same particle (i.e.,
niobium alloy powder) based on measuring randomly 50 particles or 100
particles or measuring
randomly about 1% by weight to about 2 % by weight of the batch of powder. The
measuring of
the niobium alloy particles is done using Scanning Electron Micrograph (SEM)
images. True
spherical particles have an aspect ratio of 1Ø For purposes of the present
invention, the niobium
alloy powder is considered spherical when the average aspect ratio is from 1.0
to 1.25, or from
1.0 to 1.2, or from 1.0 to 1.15, or from 1.0 to 1.1 or from 1.0 to 1.05, or
from about 1.05 to about
1.25, or from 1.05 to about 1.2, or from 1.05 to about 1.1, or about 1Ø
[0021] The niobium alloy powder of the present invention is a high purity
niobium alloy
powder, meaning the niobium alloy powder has a purity of at least 99.9 wt%
based on total
weight of the niobium alloy powder, excluding gas impurities. The purity is
with respect to the
niobium and intentional other metal(s) and/or non-gas elements present to form
the niobium
alloy. The purity level can be measured by x-ray fluorescence, Inductively
Coupled Plasma
Atomic Emission Spectroscopy (ICP-AES) or ICP Atomic Emission Spectroscopy, or
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or ICP Mass Spectrometry
or Glow
Discharge Mass Spectrometry (GDMS), Spark Source Mass Spec (SSMS) Analysis, or
any
combinations thereof The niobium alloy purity can be at least 99 wt% niobium
alloy, or at least
99.95 wt% niobium alloy, at least 99.99 wt% niobium alloy, at least 99.995 wt%
niobium alloy,
or from about 99.9 wt% niobium alloy to 99.9995 wt% niobium alloy, or from
about 99.95 wt%
niobium alloy to 99.9995 wt% niobium alloy, or from about 99.99 wt% niobium
alloy to
99.9995 wt% niobium alloy or other purity values or ranges.
[0022] The niobium alloy powder has an average particle size of from about
0.5 micron to
about 250 microns. The average particle size is determined by measuring
randomly 50 particles
using laser diffraction, or dynamic light scattering, or dynamic image
analysis techniques, such
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as an HORIBA LA-960 or LA-300 Laser Particle Size Analyzer, or a HORIBA SZ-100
Nanopartica Instrument, or an HORIBA Camsizer or Camsizer X2 dynamic image
analysis
system. The average particle size can be from about 0.5 micron to about 10
microns, or from
about 5 microns to about 25 microns, or from about 15 microns to about 45
microns, or from
about 35 microns to about 75 microns, or from about 55 microns to about 150
microns, or from
about 105 microns to about 250 microns.
[0023] The niobium alloy powder has an apparent density of from about 2
g/cc to about 18
g/cc, such as from about 2 g/cc to about 15 g/cc, or from about 2 g/cc to
about 12 g/cc or from
about 2 g/cc to about 10 g/cc, or from about 2 g/cc to about 8 g/cc, or 3 g/cc
to about 15 g/cc, or
from about 3 g/cc to about 10 g/cc, or from about 5 g/cc to about 15 g/cc, or
from about 5 g/cc to
about 10 g/cc, of from about 2.2 g/cc to about 7.8 g/cc or from about 3 g/cc
to about 7 g/cc or
from about 3.5 g/cc to about 6.5 g/cc or other apparent density numbers within
these ranges. The
apparent density is measured according to ASTM B212 standard.
[0024] The niobium alloy powder has a true density of from about 8.2 g/cc
to about 20 g/cc,
such as from about 8.2 g/cc to about 18 g/cc, or from about 8.2 g/cc to about
15 g/cc or from
about 8.2 g/cc to about 12 g/cc, or from about 8.2 g/cc to about 8 g/cc, or 9
g/cc to about 15 g/cc,
or from about 9 g/cc to about 20 g/cc, or from about 10 g/cc to about 18 g/cc,
or from about 10
g/cc to about 20 g/cc, of from about 8.5 g/cc to about 18 g/cc or from about
8.5 g/cc to about 15
g/cc or from about 8.5 g/cc to about 15 g/cc or other apparent density numbers
within these
ranges. The true density is measured according to ASTM B212 standard.
[0025] The niobium alloy powder has a Hall flow rate of 20 seconds or less.
The Hall Flow
test is conducted according to ASTM B213 standard, where the niobium alloy
powder is timed
as it flows through the orifice of a Hall Flowmeter funnel. The Hall flow rate
of the niobium
alloy powder of the present invention can be 19 seconds or less, 15 seconds or
less, 10 seconds
or less, or from 4 seconds to 20 seconds, or from 5 seconds to 20 seconds, or
from 6 seconds to
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20 seconds, or from 4 seconds to 15 seconds, or from 4 seconds to 12 seconds,
or from 5
seconds to 15 seconds, or other values in these ranges.
[0026] The niobium alloy powder can be, and preferably is plasma heat-
treated.
[0027] As stated, the niobium alloy powder of the present invention is an
alloy. The alloy
contains a) at least niobium metal and b) i) one or more other metals and/or
ii) non-metal
elements and/or iii) metalloid elements. As a further option, the niobium
alloy can be doped or
have one or more gaseous elements present as part of the alloy and/or on the
surface of the alloy.
The alloy can have a single phase. The alloy can have more than one phase.
[0028] For instance, the niobium alloy powder can be a Nb-Ti alloy or a Nb-
Si alloy or Nb-
W alloy or Nb-Mo alloy or Nb-Re alloy or a Nb-Rh alloy, or ternary Nb alloys
(e.g., containing
Nb, and two or more other metals to form the metal alloy), or other Nb-metal
alloys. The
following one or more metals can be part of the Nb alloy powder and thus be
the niobium alloy
powder of the present invention: Ti, Si, W, Mo, Re, Rh, Ta, V, Th, Zr, Hf, Cr,
Mn, Sc, Y, C, B,
Ni, Fe, Co, Al, Sn, Au, Th, U, Pu, and/or rare earth element(s). The alloy
percentages can be Nb:
30 wt% to 99.9 wt% and for the other non-Nb elements in the alloy, the wt% can
be from 0.1
wt% to 70 wt%, based on the total weight of the alloy. The Nb-alloy can be
niobium with one
other metal or element, two other metals or elements, or three or more other
metals or elements
present but not as impurities. The niobium in the Nb-alloy can be the
predominate metal (e.g.,
the niobium is the metal present in the highest percent based on the weight of
the alloy). The
niobium in the niobium alloy, as an option can be the lowest percent metal
present or not be the
predominate metal in the alloy. One further example of a Nb-alloy is C103 or
C129Y. As an
option, for the Nb-alloy of the present invention, tantalum is not present in
the alloy.
[0029] The niobium alloy powder can have various oxygen levels. For
instance, the niobium
alloy powder can have an oxygen level of 2,500 ppm or less, or 1,000 ppm or
less, or less than
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500 ppm, or less than 400 ppm, or less than 300 ppm, or less than 250 ppm, or
less than 200
ppm, such as from about 100 ppm to 495 ppm, or from about 150 ppm to about 400
ppm.
[0030] The
niobium alloy powder of the present invention can have one or more other
properties selected from the following:
- a D10 size of from about 5 microns to about 25 microns;
- a D90 size of from about 20 microns to about 80 microns; and/or
- an oxygen content of from about 10 ppm to about 1000 ppm, such as from
about 50 ppm to about 750 ppm, or from about 100 ppm to about 500 ppm or
from about 10 ppm to 100 ppm (based on weight of powder).
[0031] The
niobium alloy powder of the present invention can be a non-aggregated powder,
wherein the properties/parameters described herein are for a non-aggregated
powder.
[0032] The
niobium alloy powder of the present invention can be a non-agglomerated
powder, wherein the properties/parameters described herein are for a non-
agglomerated powder.
[0033] As
an option, the niobium alloy powder can be phosphorous doped. For instance,
the phosphorous doped levels can be at least 50 ppm, or at least 100 ppm, or,
for instance, from
about 50 ppm to about 500 ppm, and the like.
Phosphoric acid or ammonium
hexafluorophosphate and the like are suggested as the forms of phosphorus.
[0034] As
an option, the niobium alloy powder can be doped with other elements, such as
yittrium, silica, or one or more other dopants, such as gas and/or metal
dopants. The doped
levels can be at least 5 ppm, at least 10 ppm, at least 25 ppm, at least 50
ppm, or at least 100
ppm, or, for instance, from about 5 ppm to about 500 ppm, and the like. One or
more dopants
can be used for grain stabilization and/or for other property enhancements of
the powder or the
resulting article made from the powder.
[0035] The
niobium alloy powder of the present invention can be used to form articles or
portions thereof or parts thereof
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[0036] For instance, the article can be an orthopedic implant or other
medical or dental
implant. The orthopedic implant can be for a replacement of a hand, ankle,
shoulder, hip, knee,
bone, total joint reconstruction (arthroplasty), cranial facial
reconstruction, or spinal, or other
part of the human or animal body. The dental implant can be for facial
reconstruction including,
but not limited to, mandible or maxilla. The medical or dental implant finds
usefulness in
humans and other animals such as dogs, cats, and other animals.
[0037] The article can be a tracer or marker such as a medical marker, for
instance, a
radiographic Nb marker.
[0038] The article can be a surgical tool or part thereof The article can
be an augment.
[0039] The article can be an aerospace part.
[0040] The article can be a superconducting cavity.
[0041] The article can be a piping or valves used in corrosive
applications.
[0042] The article can be a boss such as a boss for a coil set used in
physical vapor
deposition processes. The boss can comprise open cellular structures and solid
structures.
[0043] The article can be any article used in metal deposition processes,
such as sputtering
targets, or portions thereof, or for structures used to hold sputtering
targets and the like. For
instance, the article can be a coil set or part thereof for physical vapor
deposition processes.
[0044] The niobium alloy powder of the present invention can be used in
spraying (e.g.,
cold spraying) of niobium alloy for coatings and/or repairs of articles or
surfaces.
[0045] The niobium alloy powder of the present invention can be used in
metal injection
molding applications and processes.
[0046] The niobium alloy powder of the present invention can be made using
a plasma heat-
treating process. For instance, a process to make the niobium alloy powder of
the present
invention can comprise, consists essentially of, consists of, or include step
a: plasma heat-
treating a starting niobium alloy powder to at least partially melt at least
an outer surface of the
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starting niobium alloy powder in an inert atmosphere to obtain a heat-treated
niobium alloy
powder, and then step b: cooling the heat-treated niobium alloy powder in an
inert atmosphere to
obtain said niobium alloy powder. The starting niobium alloy powder can be
fully melted or at
least 90% by weight melted by the plasma treatment (e.g., in the plasma torch
region of the
plasma reactor).
[0047] In the process, the starting niobium alloy powder can be an ingot-
derived niobium
alloy powder or vapor phased reduced niobium alloy powder or salt-reduced
niobium alloy
powder, or be any other source of niobium alloy powder as mentioned herein or
that is
commercially available. In the process, the starting niobium alloy powder can
be powder
metallurgy (powder-met) derived niobium alloy powder.
[0048] For instance, vapor phase-reduced particles of niobium alloy can be
obtained by
contacting and reacting one or more vaporized non-niobium chlorides mixed with
vaporized
niobium chloride with vaporized sodium. These vapor phase-reduced particles of
niobium alloy
can be composed of multiple primary particles of niobium alloy formed by the
reaction between
one or more non-niobium chlorides mixed with vaporized niobium chloride and
sodium that are
encased in the sodium chloride produced by this reaction.
[0049] As an option, the starting niobium alloy powder can be non-hydrided
or can be
hydrided before being introduced into the plasma treatment.
[0050] In the process to make the niobium alloy powder, prior to step a),
the starting
niobium alloy powder can be formed by sintering a first niobium alloy powder
to obtain a
sintered powder (which can be in the form of a sintered mass such as a green
log or other shape),
and then e-beam melting of the sintered powder or mass to obtain an ingot, and
then reducing
the ingot to the starting niobium alloy powder. The sintering can occur at
conventional sintering
temperatures for niobium alloy powder. For instance, and only as an example,
the niobium alloy
powder can be sintered at a temperature of from about 700 deg C to about 1,450
deg C (or from
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about 800 deg C to about 1,400 deg C, or from about 900 deg C to about 1,300
deg C). The
sintering time can be from 1 minute to several hours, such as from about 10
minutes to 4 hours
or from 10 minutes to 3 hours, or from about 15 minutes to about 2 hours or
from about 20
minutes to about 1 hour or other time periods. As an option, one or more heat
treatments or
sinterings can occur, whether at the same temperature, same times, or at
different temperatures
and/or different heat treatment times. The sintering can occur in an inert
atmosphere such as an
argon atmosphere. The sintering can occur in a conventional furnace used for
sintering of metal
powders.
[0051] In the option to form a niobium alloy ingot that is then reduced to
a powder, the
niobium alloy ingot can have or be any volume or diameter or shape. The
electron beam
processing can occur at a melt rate of from about 300 lbs. to about 800 lbs.
per hour using
20,000 volts to 28,000 volts and 15 amps to 40 amps, and under a vacuum of
from about 1 X
10-3 TOIT to about 1 X 10-6 Ton. More preferably, the melt rate is from about
400 lbs. to about
600 lbs. per hour using from 24,000 volts to 26,000 volts and 17 amps to 36
amps, and under a
vacuum of from about 1 X 104 TOIT to 1 X 10-5 Ton. With respect to the VAR
processing, the
melt rate is preferably of 500 lbs. to 2,000 lbs. per hour using 25 volts to
45 volts and 12,000
amps to 22,000 amps under a vacuum of 2 X 10' TOIT to 1 X 10-4 Ton, and more
preferably 800
lbs. to 1200 lbs. per hour at from 30 volts to 60 volts and 16,000 amps to
18,000 amps, and
under a vacuum of from 2 X 10' TOIT to 1 X 10-4 Ton.
[0052] The niobium alloy ingot can have a diameter of at least 4 inches or
at least 8 inches,
or have a diameter of at least 91/2 inches, at least 11 inches, at least 12
inches, or higher. For
instance, the niobium alloy ingot can have a diameter of from about 10 inches
to about 20 inches
or from about 91/2 inches to about 13 inches, or from 10 inches to 15 inches,
or from 91/2 inches
to 15 inches, or from 11 inches to 15 inches. The height or length of the
ingot can be any
amount, such as at least 5 inches or at least 10 inches or at least 20 inches,
at least 30 inches, at
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least 40 inches, at least 45 inches, and the like. For instance, the length or
height of the ingot can
be from about 20 inches to about 120 inches or from about 30 inches to about
45 inches. The
ingot can be cylindrical in shape, though other shapes can be used. After the
formation of the
ingot, optionally, the ingot can be machine cleaned using conventional
techniques. For instance,
the machine cleaning (off the surface) can result in a reduction in the
diameter of the ingot, such
as diameter reduction of from about 1% to about 10%. As a specific example,
the ingot can
have a nominal as-cast diameter of 12 inches and, due to machine cleaning, can
have a diameter
after machine cleaning of 10.75 to 11.75 inches in diameter.
[0053] The niobium alloy ingot can be reduced to a starting niobium alloy
powder by
making the ingot brittle and then crushing the ingot or subjecting the ingot
to particle reduction
steps such as milling, jaw crushing, roll crushing, cross beating and the
like. To make the ingot
brittle, the ingot can be hydrided such as by placing the ingot in a furnace
with a hydrogen
atmosphere.
[0054] With regard to the plasma heat-treating, this can also be known as
plasma treatment
or plasma processing. In the present invention, a RF plasma treatment or
induction plasma
treatment can be used. For instance, an RF thermal plasma system or an
induction plasma
reactor can be used, such as one from Tekna, Sherbrooke, QC, Canada, such as a
PL-35LS or
PL-50 or TEK-15 or other models. The central gas for the plasma can be argon,
or a mixture of
argon with other gases, or other gases such as helium and the like. The feed
rate of the central
gas can be a suitable flow such as from about 10 L/min to about 100 L/min or
from about 15
L/min to about 60 L/min or other flow rates. The sheath gas for the plasma can
be argon, or a
mixture of argon with other gases, or other gases such as other inert gases or
helium and the like.
The feed rate of the sheath gas can be a suitable flow such as from about 10
L/min to about 120
L/min or from about 10 L/min to about 100 L/min or other flow rates. The
carrier gas for the
starting niobium alloy powder can be argon, or a mixture of argon with other
gases (e.g.,
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hydrogen can be added to increase the plasma intensity), or other gases such
as other inert gases
or helium and the like. The feed rate of the carrier gas can be a suitable
flow such as from about
1 L/min to about 15 L/min or from about 2 L/min to about 10 L/min or other
flow rates. The
feeding rate of the starting niobium alloy powder into the plasma torch area
can be any flow rate,
such as from about 1 g/min of niobium alloy powder to about 120 g/min or from
about 5 g/min
to about 80 g/min of starting niobium alloy powder. Generally, a lower feed
rate of the starting
niobium alloy powder ensures more uniform and more complete spheroidal
processing of the
starting niobium alloy powder. After exiting the plasma torch area, a quench
gas can be
optionally used, such as through one or more quenching ports. The quench gas
can be any
suitable non-reactive gas, such a helium or argon. If used, the quenching gas
can be fed at a
variety of flow rates. For instance, the flow rate of the quench gas can be
from about 25 L/min to
300 L/min or from about 50 L/min to about 200 L/min or other amounts. As an
option, instead
of or in addition to using a quench gas, gravity and/or a water-cooled cooling
jacket can be used.
The designs described in U.S. Patent No. 5,200,595 and WO 92/19086 can be
used. As an
option, a passivation gas can be used after the powder is quenched or after
the powder begins to
cool down. The passivation gas can be oxygen, air, or a combination of air and
oxygen. The
flow rate of the passivation gas can be any flow rate, such as a flow rate of
from about 0.1 L/min
to about 1 L/min or other amounts. The chamber pressure of the plasma torch
can be any
suitable pressure, such as from about 0.05 NiPa to about 0.15 MPa. The plate
voltage can be
from about 5 kV to about 7.5 kV. The frequency of the RF plasma system can be
3 MHz or
other values. The plate current can be from about 2.5 A to about 4.5 A. The
power can be from
about 15 kW to about 35 kW. The distance from the plasma torch to the feeding
nozzle or the
probe position can be adjusted or varied. The distance can be 0 cm, or about 0
cm or from about
0 cm to about 8 cm. The greater the distance, the less surface evaporation of
the starting powder.
Thus, if the starting niobium alloy powder is very irregular and has aspect
ratios of over 2 or
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over 3, an option is to have the distance of the feeding nozzle close to 0 cm.
If the starting
niobium alloy powder is more regular in shape, such as having aspect ratios of
from about 1.3 to
2, the distance of the feeding nozzle can be further away from the plasma
torch as an option.
Also, a higher plasma powder setting can also be used to handle more irregular
shaped starting
niobium alloy powders.
[0055] As an option, the powder that has been plasma treated can be
collected, such as
collected under a protective atmosphere, such as an inert gas like argon. The
collected powder
can be passivated, such as using a water bath. The collected powder can be
introduced into a
water bath (e.g., submerged in a water bath).
[0056] As an option, the collected powder can be subjected to a sonication
or other powder
vibratory method to remove small particles such as nano materials deposited on
the niobium
alloy surface of the niobium alloy spheres (e.g., removing satellites and
other loose material on
the spheres). The resulting recovered niobium alloy spheres can optionally be
dried, for instance,
under a protective gas, such as an inert gas, like argon. This drying can be
at any temperature,
for instance, at a temperature of 50 deg C to 100 deg C for 10 mins to 24
hours, or 1 hour to 5
hours and the like. The recovered powder can be put in sealed bags such as
aluminum lined
anti-static bags for further use.
[0057] With the plasma treatment used in the present invention, the effort
put into creating
the particle size distribution of the starting niobium alloy powder and/or
other morphology can
carry through to the finished niobium alloy powder exiting the plasma process.
Put another way,
the size of the particle can be substantially maintained except for removing
sharp edges and/or
removing surface roughness and/or making the starting niobium alloy powder
spherical or more
spherical. Thus, prior to introducing the starting niobium alloy powder into
the plasma
treatment, the starting niobium alloy powder can be subjected to one or more
steps to achieve
desirable particle size distributions and/or other particle characteristics.
For instance, the particle
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size distribution of the starting niobium alloy powder can be such that the
D10 and/or D90 are
within 50%, or within 40%, or within 30%, or within 25%, or within 20%, or
within 15%, or
within 10% or within 5% of the D50 of that starting niobium alloy powder.
[0058] The starting niobium alloy powder prior to being introduced into the
plasma
treatment can be subjected to one or more sieving steps or other particle
screening steps, for
instance to obtain a particle size distribution as described above or other
sieve cuts, such as, but
not limited to, a minus 200 mesh cut, a minus 225 mesh cut, a minus 250 mesh
cut, a minus 275
mesh cut, a minus 300 mesh cut, and so on (with mesh being US Mesh sizes).
[0059] The starting niobium alloy powder, prior to plasma treating, can
have one of the
following particle size ranges: the average particle size can be from about
0.5 micron to about 10
microns, or from about 5 microns to about 25 microns, or from about 15 microns
to about 45
microns, or from about 35 microns to about 75 microns, or from about 55
microns to about 150
microns, or from about 105 microns to about 250 microns.
[0060] In the process to make the niobium alloy powder, the starting
niobium alloy powder
can have a first particle size distribution, and the resulting (or finished)
niobium alloy powder
(e.g., after plasma treatment) can have a second particle size distribution,
and the first particle
size distribution and the second particle size distribution are within 15% of
each other, within
10% of each other, or within 5% of each other, or within 2.5% of each other or
within 1% of
each other.
[0061] The starting niobium alloy powder prior to being introduced into the
plasma
treatment can be subjected to deoxidation treatments to remove oxygen from the
niobium alloy
powder.
[0062] The starting niobium alloy powder prior to plasma treating can be
classified or
sieved to remove various sizes, for instance, removing particles less than 20
microns, less than
15 microns, less than 10 microns, or less than 5 microns.
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[0063] After exiting the plasma treatment, the plasma-treated niobium alloy
powder can be
subjected to one or more post-processing steps.
[0064] For instance, one post-processing step can be passing the plasma-
treated niobium
alloy powder through one or more sieves to remove certain sized plasma-treated
niobium alloy
powder.
[0065] For instance, one post-processing step can be sonicating or using
other vibratory
techniques to remove imperfections from the niobium alloy spheres. For
instance, the niobium
alloy spheres from the plasma treatment can be put in a water bath and
sonicated to remove nano
materials of on the niobium alloy spheres and then the niobium alloy spheres
can be recovered.
[0066] For instance, one post-processing step can be optionally subjecting
the plasma-
treated niobium alloy to at least one deoxidation or 'deox' step. The
deoxidation can involve
subjecting the plasma-treated niobium alloy to a temperature of from about 500
C to about
1,000 C in the presence of at least one oxygen getter. For instance, the
oxygen getter can be a
magnesium metal or compound. The magnesium metal can be in the form of plates,
pellets, or
powder. Other oxygen getter material can be used.
[0067] For instance, one post-processing step can be optionally subjecting
the plasma-
treated niobium alloy to one or more heat treatment steps or annealing steps.
With regard to the
heat treating step of the plasma-treated niobium alloy, the heat treating can
occur in a
conventional oven under vacuum or under inert temperature. The heat treatment
temperature is
generally at least 800 C, or at least 1,000 C, or from about 800 C to about
1,450 C, or from
about 1,000 C to about 1,450 C, and the like. While any heat treatment time
can be used,
examples include, but are not limited to, at least 10 minutes, at least 30
minutes, from about 10
minutes to about 2 hours, or more. As an option, one or more heat treatments
can occur, whether
at the same temperature, same times, or at different temperatures and/or
different heat treatment
times. After heat-treatment, if used, the plasma-treated niobium alloy can
maintain the Hall flow
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rate achieved prior to the heat-treatment or be within 20% or within 10% or
within 5% of that
Hall flow rate.
[0068] For instance, one post-processing step can be subjecting the plasma-
treated niobium
alloy to acid leaching, such as using conventional techniques or other
suitable methods. The
various processes described in U.S. Patent Nos. 6,312,642 and 5,993,513, for
example, can be
used herein and are incorporated in their entireties by references herein. The
acid leaching can
be performed using an aqueous acid solution comprising a strong mineral acid
as the
predominant acid, for example, nitric acid, sulfuric acid, hydrochloric acid,
and the like. Also, a
hydrofluoric acid (e.g., HF) in minor amounts (e.g., less than 10% by weight,
or less than 5% by
weight, or less than 1% by weight based on the total weight of acid) can be
used. The mineral
acid concentration (e.g., HNO3 concentration) can range from about 20% by
weight to about
75% by weight in the acid solution. The acid leach can be conducted at
elevated temperatures
(above room temperature to about 100 C) or at room temperature, using acid
compositions and
techniques as shown, for example, in U.S. Patent No. 6,312,642 B 1. The acid
leach step
typically is performed under normal atmospheric conditions (e.g.,
approximately 760 mm Hg).
The acid leach step performed using conventional acid compositions and
pressure conditions,
such as indicated, can remove soluble metal oxides from the deoxidized powder
for those
conditions.
[0069] As an option, the plasma-treated niobium alloy can be nitrogen
doped. With respect
to nitrogen, the nitrogen can be in any state, such as a gas, liquid, or
solid. The powders of the
present invention, can have any amount of nitrogen present as a dopant or
otherwise present.
Nitrogen can be present as a crystalline form and/or solid solution form at
any ratio. Nitrogen
doped levels can be from 5 ppm to 5,000 ppm nitrogen or higher.
[0070] The plasma-treated niobium alloy of the present invention can be
used in a number
of ways. For instance, the plasma-treated niobium alloy can be used in
additive manufacturing
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or processing which is sometimes referred to as 3-D printing to form an
article or part of an
article. The plasma-treated niobium alloy powder of the present invention can
be used in
processes or devices that permit the use of metal powders. With the plasma-
treated powder of
the present invention, the ease of conducting additive manufacturing is
achieved. In addition or
alternatively, with the plasma-treated powder of the present invention, the
feed of the powder to
the additive manufacturing devices is improved and/or the resulting article is
more accurately
obtained from the design programmed into the printing device.
[0071] The additive processes that can utilize the plasma-treated niobium
alloy powder of
the present invention include laser powder bed fusion, electron beam powder
bed fusion,
directed energy deposition, laser cladding via a powder or wire, material
jetting, sheet
lamination, or vat photopolymerization.
[0072] Some of these additive processes are referred to as laser metal
fusion, laser sintering,
metal laser melting, or direct metal printing, or direct metal laser
sintering. In this process, a high
power laser beam is scanned over a bed of powder, sintering the powder in the
required shape, in
the path of the laser beam. After each layer, the bed is lowered by a short
distance and a new
layer of powder applied. The entire process runs in a sealed chamber with a
controlled gas
atmosphere which is either inert (e.g. argon) or active to fine-tune
material/product properties.
[0073] Some of these additive processes are referred to as laser metal
deposition (LIVID) or
near net shape. In this process, a high-power laser beam is used, connected to
a robot or gantry
system, to form a melt pool on a metallic substrate into which powder or metal
wire is fed. In
LIVID, the powder is contained in a carrier gas and directed to the substrate
through a nozzle that
is concentric with the laser beam. Alternatively, a wire can be fed from the
side. The powder or
wire is melted to form a deposit that is bonded to the substrate and grown
layer-by-layer. An
additional gas jet, concentric with the laser beam, can provide additional
shield or process gas
protection.
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[0074] Some of these additive processes are referred to as gas-metal arc
welding and plasma
welding techniques to melt the metal powder to form a 3D shape layer by layer.
In this process,
metal wire is added as the electrode melts in the arc and its droplets form
layers on the substrate.
Processes with lower heat input, such as controlled short-circuit metal
transfer, are preferred
given the heat sensitivity of most materials used in additive manufacturing.
Shielding gases
protect the layers against ambient air.
[0075] Plasma additive manufacturing is similar to laser metal deposition,
where powder is
guided towards the substrate in a gas stream and fused by the plasma heat.
[0076] Some of these additive processes are referred to as thermal
spraying. In this process,
molten, heated powder particles or droplets from molten wires are accelerated
in a gas stream
towards the substrate, where local adherence is ensured by kinetic energy and
heat. When used
for additive manufacturing, thermal spraying is applied layer-by-layer to
build up components
without geometrical complexity, e.g. tubes or reducers. Process gases protect
the hot material
against ambient atmospheric gases and help to fine-tune material properties.
[0077] Some of these additive processes are referred to as electron beam
melting or a
powder bed fusion process using an electron beam in a vacuum. This process is
similar to laser
sintering.
[0078] The additive manufacturing device or process used to form the
articles can have one
or more of the following settings: a laser power of from 150W to about 175 W
or from 155W to
165 W; a scan speed of from about 100 mm/s to about 500 mm/s, such as from
about 300 mm/s
to about 400 mm/s; hatch spacing of from about 30 microns to about 100
microns, such as from
about 80 microns to about 90 microns; a layer thickness of from about 10
microns to about 50
microns, such as from about 30 microns to about 40 microns; and/or an energy
density of from
about 3 J/mm2 to about 20 J/mm2, such as from about 4 J/mm2 to about 6 J/mm2.
Sometimes, a
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lower than maximum laser setting can be utilized so as to reduce thermal input
and/or minimize
thermal stress and/or minimize part deformation.
[0079] For additive manufacturing, preferably a niobium alloy baseplate is
utilized but other
base plates such as stainless steel or stainless steel alloys can be used.
Niobium alloy baseplates
can minimize the difference of Coefficient of Thermal Expansion (CTE) and/or
the difference in
thermal conductivities between the part and base plant. The effect can
minimize thermal residual
stresses in the part and/or can prevent lift-up of the part from the plate.
[0080] With the niobium alloy powder of the present invention and utilizing
additive
manufacturing processes, it was discovered that desirable tensile properties
of the resulting
article formed from the niobium alloy powder of the present invention can be
achieved. One or
more of these properties can be enhanced if the article is annealed such as at
a temperature of
from about 800 deg C to about 2,000 deg C (for instance for 10 mins to 10
hours, or from 30
minutes to 3 hours, or from 1 hour to 2 hours).
[0081] One or more of the following properties can be achieved with the
present invention
in forming additive manufactured (AM) objects or articles. Ultimate tensile
strength (UTS) can
be at least 50% or at least 100% greater than wrought Nb of the same shape.
The UTS can be
over 50 KSI, over 70 KSI, over 80 KSI, or over 90 KSI, such as from about 50
KSI to about 100
KSI. The Yield Stress can be at least 50% or at least 100% greater than
wrought Nb of the same
shape. The Yield Stress can be over 35 KSI, over 40 KSI, over 50 KSI, or over
80 KSI, such as
from about 35 KSI to about 90 KSI. An annealed AM article of the present
invention showed
improved Yield Stress. An annealed AM article of the present invention showed
improved
Yield Stress without compromising the UTS. Elongation can be from about 1% to
about 50%,
such as from about 3 to 40% or from 5% to 35%. An annealed AM article of the
present
invention showed improved elongation. With the present invention, a balance of
acceptable
and/or good UTS, Yield and Elongation are possible.
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[0082] With the plasma-treated niobium alloy powder utilized in additive
manufacturing,
various articles are possible and the quality and accuracy of the article can
be excellent. For
instance, the article can be an orthopedic implant or other medical or dental
implant. The
orthopedic implant can be for a replacement of a hand, ankle, shoulder, hip,
knee, bone, total
joint reconstruction (arthroplasty), cranial facial reconstruction, or spinal,
or other part of the
human or animal body. The dental implant can be for facial reconstruction
including but not
limited to mandible or maxilla. The medical or dental implant finds usefulness
in humans and
other animals such as dogs, cats and other animals.
[0083] The article can be a boss such as a boss for a coil set used in
physical vapor
deposition processes. The boss can comprise open cellular structures and solid
structures.
[0084] The article can be any article used in metal deposition processes,
such as sputtering
targets, or portions thereof, or for structures used to hold sputtering
targets and the like. For
instance, the article can be a coil set or part thereof for physical vapor
deposition processes.
[0085] As an option, the plasma-treated niobium alloy can be further
processed to form a
capacitor electrode (e.g., capacitor anode). This can be done, for example, by
compressing the
plasma treated powder to form a body, sintering the body to form a porous
body, and anodizing
the porous body. The pressing of the powder can be achieved by any
conventional techniques
such as placing the powder in a mold and subjecting the powder to a
compression by use of a
press, for instance, to form a pressed body or green body. Various press
densities can be used,
and include, but are not limited to, from about 1.0 g/cm3 to about 7.5 g/cm3.
The powder can be
sintered, anodized, and/or impregnated with an electrolyte in any conventional
manner. For
instance, the sintering, anodizing, and impregnation techniques described in
U.S. Patent Nos.
6,870,727; 6,849,292; 6,813,140; 6,699,767; 6,643,121; 4,945,452; 6,896,782;
6,804,109;
5,837,121; 5,935,408; 6,072,694; 6,136,176; 6,162,345; and 6,191,013 can be
used herein and
these patents are incorporated in their entirety by reference herein. The
sintered anode pellet can
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be, for example, deoxidized in a process similar to that described above for
the powder. The
anodized porous body further can be impregnated with manganese nitrate
solution, and calcined
to form a manganese oxide film thereon. Wet valve metal capacitors can use a
liquid electrolyte
as a cathode in conjunction with their casing. The application of the cathode
plate can be
provided by pyrolysis of manganese nitrate into manganese dioxide. The pellet
can be, for
example, dipped into an aqueous solution of manganese nitrate, and then baked
in an oven at
approximately 250 C or other suitable temperatures to produce the manganese
dioxide coat.
This process can be repeated several times through varying specific gravities
of nitrate to build
up a thick coat over all internal and external surfaces of the pellet. The
pellet optionally can be
then dipped into graphite and silver to provide an enhanced connection to the
manganese
dioxide cathode plate. Electrical contact can be established, for example, by
deposition of carbon
onto the surface of the cathode. The carbon can then be coated with a
conductive material to
facilitate connection to an external cathode termination. From this point the
packaging of the
capacitor can be carried out in a conventional manner, and can include, for
example, chip
manufacture, resin encapsulation, molding, leads, and so forth.
[0086] As part of forming an anode, for example, a binder, such as camphor
(CioH160) and
the like, can be added to the powder, for instance, in the amount of 3-5 wt%
based on 100 wt%
of the powder and the mixture can be charged into a form, compression-molded,
and sintered by
heating for 0.3-1 hour at 1,000-1,400 C while still in a compressed state.
Such a molding
method makes it possible to obtain pellets consisting of sintered porous
bodies.
[0087] When a pellet obtained using the above-described molding process is
employed as a
capacitor anode, before the powder is compression-molded, it is preferable to
embed lead wires
into the powder in order to integrate the lead wires into the pellet.
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[0088] The capacitor can be manufactured using the above-described pellet.
A capacitor
equipped with an anode can be obtained by oxidizing the surface of the pellet,
a cathode facing
the anode, and a solid electrolyte layer disposed between the anode and
cathode.
[0089] A cathode terminal is connected to the cathode by soldering and the
like. In
addition, an exterior resin shell is formed around a member composed of the
anode, cathode, and
solid electrolyte layer. Examples of materials used to form the cathode
include graphite, silver,
and the like. Examples of materials used to form the solid electrolyte layer
include manganese
dioxide, lead oxide, electrically conductive polymers, and the like.
[0090] When oxidizing the surface of a pellet, for example, a method can be
used that
involves treating the pellet for 1-3 hours in an electrolyte solution such as
nitric acid, phosphoric
acid and the like with a concentration of 0.1 wt% at a temperature of 30-90 C
by increasing the
voltage to 20-60V at a current density of 40-120 mA/g. A dielectric oxide film
is formed in the
portion oxidized at such time.
[0091] As indicated, the plasma-treated niobium alloy of the present
invention can be used
to form a capacitor anode (e.g., wet anode or solid anode). The capacitor
anode and capacitor
(wet electrolytic capacitor, solid state capacitor, etc.) can be formed by any
method and/or have
one or more of the components/designs, for example, as described in U.S.
Patent Nos.
6,870,727; 6,813,140; 6,699,757; 7,190,571; 7,172,985; 6,804,109; 6,788,523;
6,527,937 B2;
6,462,934 B2; 6,420,043 Bl; 6,375,704 Bl; 6,338,816 Bl; 6,322,912 Bl;
6,616,623; 6,051,044;
5,580,367; 5,448,447; 5,412,533; 5,306,462; 5,245,514; 5,217,526; 5,211,741;
4,805,704; and
4,940,490, all of which are incorporated herein in their entireties by
reference. The powder can
be formed into a green body and sintered to form a sintered compact body, and
the sintered
compact body can be anodized using conventional techniques. It is believed
that capacitor
anodes made from the powder produced according to the present invention have
improved
electrical leakage characteristics. The capacitors of the present invention
can be used in a
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variety of end uses such as automotive electronics; cellular phones; smart
phones; computers,
such as monitors, mother boards, and the like; consumer electronics including
TVs and CRTs;
printers/copiers; power supplies; modems; computer notebooks; and disk drives.
[0092] Further details of the starting niobium alloy powder, the plasma-
treated niobium
alloy powder, and components formed from the niobium alloy powder are provided
below and
further form optional aspects of the present invention.
[0093] With the methods of the present invention, the niobium alloy powder
can be made
that can have:
a) an apparent density of from about 2 g/cc to about 18 g/cc,
b) a D10 particle size of from about 5 microns to about 25 microns,
c) a D50 particle size of from about 20 microns to about 50 microns,
d) a D90 particle size of from about 30 microns to about 100 microns, and/or
e) a BET surface area of from about 0.05 m2/g to about 20 m2/g.
The niobium alloy powder can have at least one of the following properties:
a) an apparent density of from about 3 g/cc to about 18 g/cc,
b) a D10 particle size of from about 12 microns to about 25 microns,
c) a D50 particle size of from about 20 microns to about 40 microns,
d) a D90 particle size of from about 30 microns to about 70 microns, and/or
e) a BET surface area of from about 0.1 m2/g to about 15 m2/g.
[0094] For purposes of the present invention, at least one of these
properties, at least two, at
least three, at least four, or all five properties can be present.
[0095] In at least one embodiment of the present invention, the plasma-
treated niobium
alloy powder (or starting niobium alloy powder) can have the following
characteristics, but it is
to be understood that the powder can have characteristics outside of these
ranges:
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Purity levels:
- Oxygen content of from about 10 ppm to about 60,000 ppm, such as from
about 10 ppm to about 100 ppm, or from about 25 ppm to about 150 ppm, or from
about 25
ppm to about 500 ppm, or 10 ppm to 1,000 ppm, or from about 250 ppm to about
50,000 ppm
or from about 500 ppm to about 30,000 ppm, or from about 1000 ppm to about
20,000 ppm
oxygen. An oxygen (in ppm) to BET (in m2/g) ratio can be from about 2,000 to
about 4,000,
such as from about 2,200 to about 3,800, from about 2,400 to about 3,600, from
about 2,600
to about 3,400, or from about 2,800 to about 3,200, and the like.
- A carbon content of from about 1 ppm to about 100 ppm (e.g. from about 10
ppm to about 50 ppm or from about 20 ppm to about 30 ppm carbon).
- A nitrogen content of from about 100 ppm to about 20,000 ppm or higher
(e.g.
from about 1,000 ppm to about 5,000 ppm or from about 3,000 ppm to about 4,000
ppm or
from about 3,000 ppm to about 3,500 ppm nitrogen).
- A hydrogen content of from about 1 ppm to about 1,000 ppm (e.g. from
about
300 ppm to about 750 ppm, or from about 400 ppm to about 600 ppm hydrogen).
- An iron content of from about 1 ppm to about 50 ppm (e.g. from about 5
ppm
to about 20 ppm iron).
- A nickel content of from about 1 ppm to about 150 ppm (e.g. from about 5
ppm to about 100 ppm or from about 25 ppm to about 75 ppm nickel).
- A chromium content of from about 1 ppm to about 100 ppm (e.g. from about
5
ppm to about 50 ppm or from about 5 ppm to about 20 ppm chromium).
- A sodium content of from about 0.1 ppm to about 50 ppm (e.g. from about
0.5
ppm to about 5 ppm sodium).
- A potassium content of from about 0.1 ppm to about 100 ppm (e.g. from
about
ppm to about 50 ppm, or from about 30 ppm to about 50 ppm potassium).
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- A magnesium content of from about 1 ppm to about 50 ppm (e.g. from about
5
ppm to about 25 ppm magnesium).
- A phosphorus (P) content of from about 5 ppm to about 500 ppm (e.g. from
about 100 ppm to about 300 ppm phosphorus).
- A fluoride (F) content of from about 1 ppm to about 500 ppm (e.g. from
about
25 ppm to about 300 ppm, or from about 50 ppm to about 300 ppm, or from about
100 ppm
to about 300 ppm).
[0096] The plasma treated powder (or starting niobium alloy powder)
(primary, secondary,
or tertiary) can have a particle size distribution (based on overall %) as
follows, based on mesh
size:
- +60# of from about 0.0 to about 1% and preferably from about 0.0 to about
0.5% and more preferably 0.0 or about 0Ø
- 60/170 of from about 45% to about 70% and preferably from about 55% to
about 65%, or from about 60% to about 65%.
- 170/325 of from about 20% to about 50% and preferably from about 25% to
about 40% or from about 30% to about 35%.
- 325/400 of from about 1.0% to about 10% and preferably from about 2.5% to
about 7.5% such as from about 4 to about 6%.
- -400 of from about 0.1 to about 2.0% and preferably from about 0.5% to
about
1.5%.
[0097] The plasma-treated niobium alloy powder of the present invention can
also have a
pore size distribution which can be unimodal or multi-modal, such as bi-modal.
[0098] The plasma-treated niobium alloy powders of the present invention
can have a BET
surface area of from about 0.01 m2/g to about 20 m2/g, and more preferably
from about 0.05
m2/g to about 5 m2/g such as from about 0.1 m2/g to about 0.5 m2/g.
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[0099] The starting niobium alloy powder may comprise primary particles
that have an
average size in the range of 1 nm to about 500 nm, or 10 nm to 300 nm, or 15
nm to 175 nm, or
20 nm to 150 nm, or 25 nm to 100 nm, or 30 nm to 90 nm, or other sizes. The
average size and
distribution of the primary particles sizes can depend on the method of
preparation. The primary
particles may tend to form clusters or agglomerates of larger size than the
primary particles. The
shapes of raw or starting niobium alloy powder particles may include, but are
not limited to,
flaked, angular, nodular, or spherical, and any combinations thereof or
variations thereof The
raw powder used to practice the present invention can have any purity with
respect to the
niobium alloy metal with higher purities being preferred. For instance, the
niobium alloy purity
(e.g., by wt%) of the raw or starting powder can be 95% Nb-alloy or greater,
or 99% Nb-alloy or
greater such as from about 99.5% Nb-alloy or greater and more preferably
99.95% Nb-alloy or
greater and even more preferably 99.99% Nb-alloy or greater, or 99.995% Nb-
alloy or greater or
99.999% Nb-alloy or greater.
[0100] At any stage, before or after plasma-treatment, the niobium alloy
powder can be
passivated using an oxygen-containing gas, such as air, as part of the plasma-
treated niobium
alloy powder production process of the present invention. Passivation
typically is used to form a
stabilizing oxide film on the powder during processing and in advance of
sintered body
formation using the powder. A powder production process of the present
invention therefore can
include hydrogen doping and passivating operations.
[0101] Passivating the niobium alloy powder can be by any suitable method.
Passivation
can be achieved in any suitable container, for example, in a retort, a
furnace, a vacuum chamber,
or a vacuum furnace. Passivation can be achieved in any of the equipment used
in processing,
such as heat treating, deoxidizing, nitriding, delubing, granulating, milling,
and/or sintering, the
metal powder. The passivating of the metal powder can be achieved under
vacuum. Passivation
can include backfilling of the container with an oxygen containing gas to a
specified gas
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pressure, and holding the gas in the container for a specified time. The
oxygen content level of
the gas used in powder passivation can be from 1 to 100 wt% oxygen, or from 1
to 90 wt%, or
from 1 to 75 wt%, or from 1 to 50 wt%, or from 1 to 30 wt%, or from 20 to 30
wt%, or an
oxygen content that is the same as or greater than that of air or atmospheric
air, or other content
levels. The oxygen can be used in combination with an inert gas, such as
nitrogen, argon, or
combinations of these, or other inert gases. The inert gas does not react with
the niobium alloy
during the passivation process. The inert gas, such as nitrogen gas and/or
argon gas, preferably
can compose all or essentially all (e.g., >98%) of the remaining portion of
the passivating gas
other than the oxygen. Air can be used as the passivating gas. Air can refer
to atmospheric air or
dry air. The composition of dry air typically is nitrogen (about 75.5 wt%),
oxygen (about 23.2
wt%), argon (about 1.3 wt%), and the rest in a total amount of less than about
0.05%. The
content level of hydrogen in dry air is about 0.00005 vol%.
[0102] Additional techniques that may be employed for the passivation
process can be
adapted from those disclosed in U.S. Pat. No. 7,803,235, which is incorporated
in its entirety by
reference herein.
[0103] The present invention includes the following
aspects/embodiments/features in any
order and/or in any combination:
1. Niobium alloy powder comprising
a. a spherical shape wherein the powder has an average aspect ratio of from
1.0
to 1.25;
b. a purity of niobium alloy of at least 99.99 wt% Nb-alloy based on total
weight
of said niobium alloy powder, excluding gas impurities;
c. an average particle size of from about 0.5 micron to about 250 microns;
d. a true density of from 8.2 g/cc to 20 g/cc;
e. an apparent density of from about 2 g/cc to about 18 g/cc; and
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f. a Hall flow rate of 20 sec or less.
2. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder is plasma heat-treated.
3. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder has an oxygen level of less than 400 ppm.
4. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder has an oxygen level of less than 300 ppm.
5. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder wherein said average aspect ratio is from
1.0 to 1.1.
6. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder wherein said average aspect ratio is from
1.0 to 1.05.
7. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said purity is at least 99.995 wt% Nb-alloy.
8. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 0.5 micron to about 10
microns.
9. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 5 microns to about 25
microns.
10. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 15 microns to about 45
microns.
11. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 35 microns to about 75
microns.
12. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 55 microns to about 150
microns.
13. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said average particle size is from about 105 microns to about 250
microns.
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14. The niobium alloy powder of any preceding or following
embodiment/feature/aspect,
wherein said niobium alloy powder has at least one of the following
properties:
a. a D10 size of from about 5 microns to 25 microns;
b. a D90 size of from about 20 microns to 80 microns; and/or
c. an oxygen content of from about 100 ppm to about 1000 ppm, such as from
about 100 ppm to about 250 ppm.
15. An article comprising the niobium alloy powder of any preceding or
following
embodiment/feature/aspect.
16. The article of any preceding or following embodiment/feature/aspect,
wherein said
article is a boss for a coil set for a physical vapor deposition process.
17. The article of any preceding or following embodiment/feature/aspect,
wherein said boss
comprises open cellular structures and solid structures.
18. The article of any preceding or following embodiment/feature/aspect,
wherein said
article is a coil set or part thereof for a physical vapor deposition process.
19. The article of any preceding or following embodiment/feature/aspect,
wherein said
article is an orthopedic implant or part thereof.
20. The article of any preceding or following embodiment/feature/aspect,
wherein said
article is a dental implant.
21. A method for forming an article, said method comprising additive
manufacturing said
article by utilizing the niobium alloy powder of any preceding or following
embodiment/feature/aspect to form the shape of said article or part thereof
22. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises laser powder bed fusion.
23. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises electron beam powder bed fusion.
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24. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises directed energy deposition.
25. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises laser cladding via a powder or wire.
26. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises material jetting.
27. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises sheet lamination.
28. The method of any preceding or following embodiment/feature/aspect,
wherein said
additive manufacturing comprises vat photopolymerization.
29. A method to make to the niobium alloy powder of any preceding or
following
embodiment/feature/aspect, said method comprising:
a. plasma heat-treating a starting niobium alloy powder to at least partially
melt
at least an outer surface of said starting niobium alloy powder in an inert
atmosphere to obtain a heat-treated niobium alloy powder, and
b. cooling said heat-treated niobium alloy powder in an inert atmosphere to
obtain said niobium alloy powder.
30. The method of any preceding or following embodiment/feature/aspect,
wherein said
starting niobium alloy powder is ingot-derived niobium alloy powder.
31. The method of any preceding or following embodiment/feature/aspect,
wherein said
starting niobium alloy powder is a powder-net niobium alloy powder.
32. The method of any preceding or following embodiment/feature/aspect,
wherein said
starting niobium alloy powder has a first particle size distribution, and said
niobium alloy
powder has a second particle size distribution, and said first particle size
distribution and said
second particle size distribution are within 10% of each other.
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33. The
method of any preceding or following embodiment/feature/aspect, wherein prior
to
step a, the starting niobium alloy powder is formed by sintering a first
niobium alloy powder
to obtain a sintered powder, and then e-beam melting of said sintered powder
to obtain an
ingot, and then reducing said ingot to said starting niobium alloy powder.
[0104] The
present invention can include any combination of these various features or
embodiments above and/or below as set forth in sentences and/or paragraphs.
Any combination
of disclosed features herein is considered part of the present invention and
no limitation is
intended with respect to combinable features.
[0105]
Applicant specifically incorporates the entire contents of all cited
references in this
disclosure. Further, when an amount, concentration, or other value or
parameter is given as
either a range, preferred range, or a list of upper preferable values and
lower preferable values,
this is to be understood as specifically disclosing all ranges formed from any
pair of any upper
range limit or preferred value and any lower range limit or preferred value,
regardless of whether
ranges are separately disclosed. Where a range of numerical values is recited
herein, unless
otherwise stated, the range is intended to include the endpoints thereof, and
all integers and
fractions within the range. It is not intended that the scope of the invention
be limited to the
specific values recited when defining a range.
[0106]
Other embodiments of the present invention will be apparent to those skilled
in the
art from consideration of the present specification and practice of the
present invention disclosed
herein. It is intended that the present specification and examples be
considered as exemplary
only with a true scope and spirit of the invention being indicated by the
following claims and
equivalents thereof
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